Dual-Use of Image Space: The Challenges of Explaining Visualizations from Within

In this paper we discuss a technique for presenting textual information within visualizations and for enabling users to interact with the text. Our method relies on shading images using text-based dither matrices; users extract text by effectively enlarging the dither matrices to the point where text becomes legible. Transitions between matrix sizes are carried out step by step and can be implemented at interactive rates so that the process of extracting text is seen as an animation. Presenting text explanations in the image space poses as number of legibility and text layout challenges mainly because on one hand text is usually written and read from rectangular windows and on the other hand, the silhouette of graphical objects have irregular shapes. In the paper we discuss the challenges and their respective solutions in detail.